The present invention relates to a moving-coil linear motor.
A prior art moving-coil linear motor is, as shown in FIG. 22, provided with a field permanent magnet 11 secured at a fixing portion and a comb teeth-like armature core 12 opposed to the field permanent magnet 11. The comb teeth-like armature core 12 has armature coils 13 divided and wound therein. In the armature core 12 having the wound armature coils 13, where the number of phases is n, the number of field permanent magnets 11 is p, and the number of teeth 14 corresponding to one pole is q, the number N of teeth provided in the armature core 12 is:
N=nxc3x97pxc3x97q
In the armature coil 12 which has a number of teeth formed equidistantly, three-phase windings U, V, and W of the armature coil 13 are wound with at least two tooth pitches skipped.
Therefore, the moving-coil linear motor is such that the magnetic circuit of a moving armature core 12 is not endless and is open at both ends thereof, whereby slots at both sides in the rotor thrust direction accommodate one coil, differing from the slots at the central portion. And, an edge effect occurs due to the slots, wherein a cogging thrust TC of one cycle is generated in the magnetic pole pitch of field magnets 11, thereby causing unevenness in the thrust.
Also, where a temperature sensor is inserted into a slot accommodating a coil in order to control the temperature of the coils, it is necessary to make the slot large, whereby the armature core is increased in size, and such a problem occurs, by which the ratio of occupancy of windings is lowered. Therefore, although the temperature sensor is provided at both ends of the coils in the linear motors, the temperature of the central portion of the coil cannot be measured, wherein only inaccurate temperature detection was possible.
The present invention solves such problems resulting from the cogging thrust, and it is therefore an object of the invention to provide a linear motor in which the detection accuracy of the coil temperature can be improved.
Therefore, in the invention, the armature core is divided into a plurality of block cores, and teeth secured at the respective block cores equidistantly from one another are provided with armature coils wound in the form of lumped winding, and the block cores are disposed in the thrust direction where spacing corresponding to an electrical angle greater by an integer number of times than a value which is obtained by dividing the electrical angle 180xc2x0 of the magnet pitch by the number of divisions is secured between the block cores, wherein the armature coils of the block cores between which the spacing is secured are wound so that their phases shift by the electrical angle corresponding to the spacing.
Therefore, phases of the cogging thrust generated due to the armature coils of the respective block cores are subjected to phase shifts at the electrical angle in response to the spacing one after another, whereby the cogging thrusts generated in the respective block cores can be mutually counterbalanced and are zeroed by each other. Therefore, the winding can be constituted by a complete three-phase balanced winding, and it is possible to insert a temperature sensor in the spacing between the block cores.
The armature core is divided into three block cores, that is, the armature core is provided with the first block core, second block core, and third block core, each of which has nine teeth having a length longer by eight times than the magnet pitch at equal intervals, and is provided with a three-phase armature coil wound in the form of lumped winding with the teeth of the respective block cores divided into three groups, a spacing equivalent to two-thirds the magnet pitch is provided between the respective block cores, and is disposed in the thrust direction, wherein the first block core is divided into three groups to form U, V and W phases in that order, in which an armature coil is wound, the second block core is divided into three groups to form V, W and U phases in the order, in which an armature coil is wound, and the third block core is divided into three groups to form W, U and V phases in that order, in which an armature coil is wound, whereby the respective phase coils are connected in equilibrium to each other.
The three block cores are disposed in the thrust direction with a spacing of one-third the magnet pitch secured between the three block cores, and teeth are divided into three groups, wherein an armature coil may be wound in the respective groups in the order of U, V and W phases in the first block core, an armature coil maybe wound, with the winding direction reversed, in the respective groups in the order of W, U and V phases in the second block core, and an armature coil may be wound, in the same direction as that in the first block core, in the order of V, W and U-phases in the third block core.
Also, the armature core is divided into two block cores, wherein the first block core is provided with nine teeth, longer by eight times than the magnet pitch, at equal intervals, the second block core of the same configuration as that of the first block core is disposed in the thrust direction with a spacing of one half the magnet pitch secured between the block cores, and teeth of the first block core are divided into three groups and an armature coil is wound in the order of U, V, and W phases, wherein in the second block core, the V-phase coil is wound in one tooth, the W-phase coil is wound in the next three teeth as a group, the U phase coil is wound in the further next three teeth as a group, and the V-phase coil is wound in the remaining two teeth.
Further, as a means to bring about similar effects, there is a means in which the second block core is divided into three groups, and an armature coil is wound in the order of V phase and W phase so that the phase of the magnetomotive force vector is electrically shifted by 120xc2x0 from that of the first block core.
Also, in any case, a spacing piece of a magnetic substance is inserted in the clearance between the block cores to retain the spacing, and a temperature sensor such as a thermister or a thermal protector is inserted into the clearance, and it is possible to control the temperature of the coils.
Thus, according to the invention, in a moving coil linear motor, the armature core of the rotor is divided into a plurality of block cores which will be disposed in the thrust direction, the respective block cores are provided with teeth divided into groups equivalent to the number of phases disposed at equal intervals, and the block cores are disposed in the thrust direction in a state where they are placed in the thrust direction with a spacing greater by an integer number of times by which the magnet pitch is divided by the number of divisions between the block cores. Since the phase of the armature coil of the respective core is caused to shift by an electrical angle corresponding to the abovementioned spacing, the armature coil can be wound in the form of lumped winding on the teeth, and the cogging thrust resulting from the edge effect of the rotor can be counterbalanced to zero the cogging thrust, whereby it is possible to obtain a highly accurate linear motor.
The rotor is divided into three block cores, which are disposed in the thrust direction at a spacing equivalent to two-thirds or one-third of the magnet pitch, the respective block cores are caused to have nine teeth longer by eight times than the magnet pitch, and they are divided into three groups to form a winding, wherein a coil is directly wound on the teeth in the form of lumped winding, and the flux linkage is large. Further, 3-phase balanced connection can be secured.
Also, the rotor may be divided into two block cores, which may be disposed at intervals equivalent to one half of the magnet pitch, and the respective armature coils are caused to differ in phase by 90xc2x0 from each other, and where the cogging thrusts of the same phase are connected to each other in series, the circulating current resulting from the phase difference in the magnetomotive force can be removed, and it is possible to obtain a highly efficient linear motor. The armature coil of the respective block core is caused to shift by an electrical angle corresponding to the spacing, whereby it is possible to directly wind the armature coil on the teeth in the form of lumped winding, and there is an effect by which the cogging thrust resulting from the edge effects of the rotor can be zeroed by mutually counterbalancing the same in the respective block cores. Therefore, a highly accurate linear motor can be obtained.
The rotor is divided into three block cores which will be disposed in the thrust direction at a spacing equivalent to two-thirds or one-third of the magnet pitch, and nine teeth are provided, with a length longer by eight times than the magnet pitch, which are divided into three groups and are, respectively, provided with winding, whereby, since the winding is wound directly on the teeth to secure a lumped winding, the flux linkage is increased, and three-phase balanced connection can be obtained.
Also, the rotor is divided into two block cores which are disposed at intervals equivalent to one half of the magnet pitch. Where the respective armature coils are connected with the same phase cogging thrusts placed in series in a state where the respective armature coils are placed with a difference of 90xc2x0 in phase, a circulating current resulting from a difference in the electromotive force is removed, and a highly efficient linear motor can be obtained.
Further, it is possible to detect the temperature of the intermediate coil portions by providing a temperature sensor in the clearance, whereby it is possible to accurately control the temperature of the coils in a linear motor. Also, if the clearance incorporating the temperature sensor is integrated by resin molding, and retaining of the temperature sensor becomes reliable, wherein an advantage can be obtained by which the detection accuracy of the temperature can be improved.
Also, by engaging and connecting the teeth, which constitute the block cores, with engagement projections and fitting portions of an iron relay part, the teeth can be easily punched out, whereby the teeth on which coils are wound can be linked with each other, and it becomes easy to carry out the winding work.